Mojo: Add support for speciying handle<data_pipe_{consumer,producer}> in a .mojom file.

Fix support for arrays of handles.

BUG=329648,329647
R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/98333007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242201 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242201